What does the flu mean for the 6th COVID-19 wave in Quebec?

Flu infections once again reached epidemic levels in early April, meaning the proportion of positive tests for the virus has surpassed five percent. That has now reached 11 per cent, a level typically seen in January and February in Quebec.

“It’s very unusual to have a flu epidemic begin so late in the year,” said Dr. Guy Boivin, a microbiologist and infectious diseases specialist based at the Center Hospitalier Universitaire de Québec, a network of teaching hospitals in Quebec City.

“We are in a situation that is completely out of the ordinary. The pandemic really upends all the theories we have about flu epidemics.”

Boivin and his team of researchers at the Université Laval in Quebec City, along with Swiss researcher Clément Fage, published a study earlier this year about how the influenza virus and SARS-CoV-2, the virus that causes COVID-19, interact with each other.

Viruses repel each other: study

The scientists found that the viruses appear to repel each other. After first infecting nasals cells with one virus, it was a lot harder to infect them with the other, and vice versa, according to the study.

Boivin said the team’s hypothesis is that, at a population level, their findings could mean the resurgence of the flu could contribute to a reduction in the number of COVID-19 cases in the coming weeks.

Still, Boivin cautions, that repulsion isn’t absolute.

“Some people can still be co-infected by both viruses and we need to keep a close eye on that,” he said, noting there have been cases reported in Europe and even recently in Quebec where people have been infected by both the influenza virus and SARS-CoV-2 at the same time.

A British study found that such “co-infections” can lead to symptoms that are more severe.

“We can expect harmful effects from being infected by both viruses simultaneously,” Boivin said.

He explained that the unusually late flu epidemic may be a result of loosening pandemic restrictions, though the exact causes remain unclear.

While COVID-19 is considered more contagious and more dangerous, the flu can kill hundreds of people per year. In 2018, more than 1,000 Quebecers died after being infected with the virus.

In a news conference last Thursday, interim public health director Dr. Luc Boileau said people with flu symptoms should take the same precautions as they would for COVID-19 — including isolating for five days after the onset of symptoms, wearing a mask to minimize contaminating others, and avoiding public gatherings and people at increased risk for the following five days.